Behind countryman David de Gea, Valdes only managed two Premier League appearances after officially switching to United in January - but Van Gaal revealed the 33-year-old is unlikely to see out his 18-month contract.

Van Gaal did not select Valdes for United's participation in the International Champions Cup, which will see them take on the likes of America, San Jose Earthquakes, Barcelona and Paris Saint-Germain.

"Valdes is not selected because he doesn't follow my philosophy. The philosophy is how you play football and how you maintain your match rhythm," Van Gaal told a news conference in Seattle, where United play America on Friday.

"He refused last year to play in the second team.

"There are a lot of other aspects in the philosophy how you have to play like a goalkeeper at Manchester United.

"When you are not willing [to apply] the principles of that philosophy there is only one way, and that is out.

"For us this is a big disappointment. We thought he would follow our philosophy.

"It's a pity because we have given the opportunity to rehabilitate [in October]. Then we gave a contract. Then of course he is fit to play. When you're not playing in the first selection, you have to play in the second selection."

Van Gaal's comments seemingly sew up De Gea's future for the 2015-16 season at least, but the Dutch tactician also could not confirm the 24-year-old's stance - with Real Madrid rumours circulating.

"When you ask me about the attitude of De Gea, I think it's stupid," Van Gaal said, referring to the journalist's question.

"I cannot answer that [if Manchester United will sign Sergio Romero] because it is a process.

"I can't say anything about the process and the strategy of Manchester United. I've said that two or three press conferences and you are asking every time the same questions.

"Maybe you are right [about Romero], or maybe not, it's dependable on David de Gea.

"Shall he stay? I don't know.

"Maybe you? Maybe you have spoken with David? He's training here and doing his utmost best."